Field of the Invention
The present invention relates to a slurry composition used for the planarization technique by Chemical Mechanical Polishing (hereinafter, referred to as “CMP”) which is one step of a process of manufacturing a semiconductor device, and a method of using the same.
Description of Related Art
In a process of manufacturing a semiconductor device, a multi-layered laminated structure in which many layers of an insulating film, a metal film and the like is generally formed on a shallow trench isolation film on a substrate. Generally, upon multi-layered lamination, it is necessary to deposit an interlayer dielectric film or a metal film on the substrate after the shallow trench isolation film, to subject the produced irregularities to a planarization treatment through chemical mechanical polishing (CMP), and to laminate a new wiring layer on the planarized surface.
Recently, as the miniaturization of a semiconductor device progresses in each layer of a multi-layered laminated structure on a substrate, planarization at an increasingly higher precision becomes necessary. For this reason, the need for a CMP step is intensifying, and a planarization step by CMP becomes important in a process of manufacturing a semiconductor device.
As for a polishing slurry composition used in this CMP step, recently, one containing alumina as a metal oxide polishing particle has been used for a hard metal film, such as a tungsten film and the like, and a polishing slurry containing silica as a polishing particle has been used for a soft metal film, such as copper and the like. In such a polishing slurry, alumina and silica are mixed together with an additive for controlling a selective ratio between a metal film, a barrier film or an oxide film. In addition, in planarization polishing of an interlayer dielectric film and a shallow trench isolation film, silica particles and ceria particles are used as the polishing particle. In such a polishing slurry composition, since silica particles only have a mechanical polishing function, a polishing rate (processing rate) improving additive, such as potassium hydroxide and ammonia, may be added to the slurry composition. On the other hand, since ceria particles cause a slight chemical reaction with the SiO2 surface, which is a component of a film, it is not as necessary to use an additive. Furthermore, the use of ceria particles provide a rapid processing rate. For this reason, a polishing slurry composition containing ceria is expected to perform better and has been initiated in industrial use as a means to improve throughput.
It has been known that the planarization property is not better when using a polishing slurry in which only the metal oxide particle has been dispersed. For this reason, besides metal oxide particles, various additives, for example, surfactants, water-soluble organic polymers, organic acids, and chelating agents, have been used for the purpose of improving planarization.
For example, it has been known that when a water-soluble organic polymer, such as polyethylene oxide, polyvinyl alcohol, alginates, guar gum, carboxylmethylcellulose, hydroxylethylcellulose and polyacrylate, is added to a polishing slurry composition with metal oxide particles dispersed in water, dishing is less likely to occur when polishing the layers of interlayer dielectric film, shallow trench isolation film, and the metal film due to the improved planarization effect.
However, problems can develop when the substrate surface layers are polished and planarized with such a polishing slurry composition under a polishing pressure and a platen rotating rate normally adopted in CMP. As a water-soluble organic polymer is added to a slurry composition, there is a tendency for the processing rate to decrease. Also, when the thickness of the substrate surface layers to be polished is small, the polishing rate is reduced. At the same time, scratching occurs, and planarization deteriorates noticeably.
For example, the use of the following slurry compositions are known: a polishing slurry containing a ceria particle as a polishing particle and ammonium polycarboxylate as a water-soluble organic polymer (see Japanese Patent No. 3278532, which is incorporated by reference); a polishing slurry composition containing an alumina particle as a polishing particle and polyacrylic acid as a water-soluble organic polymer (see Japanese Patent No. 3130279, which is incorporated by reference); and a cerium oxide polishing slurry containing a cerium oxide particle, a copolymer of ammonium acrylate and methyl acrylate, and water (see JP-A 2000-17195, which is incorporated by reference). However, scratching increases when the substrate surface layers are polished and planarized through the use of one of the above polishing slurry compositions, even though dishing is prevented and planarization improves.
For this reason, it was necessary to perform a final polishing step using another slurry, such as one with small, soft particles, such as silica, after the aforementioned polishing and planarization steps in many cases, to remove the scratches created by the use of the previously mentioned slurry compositions. Because of the scratching problems, it became necessary to incorporate this time-consuming additional polishing step to remove the scratches, which typically includes the removal of the polishing slurry composition used in the former planarization polishing step, the washing of the polishing apparatus and pad, and the preparation and use of the slurry for the final polishing step. Alternatively, if another polishing apparatus is used for the final polishing step than the one used in the previous planarization polishing step, the polished substrates need to be transferred from one polishing apparatus to another, which is economically costly as well as time consuming.
Unlike the case where scratches are from the dresser, a pad dust and the like, scratches created by the polishing slurry composition cannot be solved by improving control of the polishing apparatus and work procedures without fundamentally improving the polishing slurry composition. Reducing the occurrence of scratches is an important goal in planarizing a device. The attainment of this goal becomes more important as miniaturization of a device becomes indispensable. For example, various problems that retard the manufacturing process, such as an increase in the resistance and breaking of the wire due to flawed wiring and a flawed interlayer dielectric film such as an easily flawed low-k film, can be resolved by reducing the occurrences of scratching.
Therefore, it is desirable to have a polishing slurry composition that effectively reduces the occurrences of scratching and a method of polishing that reduces the occurrences of scratching while realizing an economical polishing step.